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S95-05

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S95-05 [#permalink]

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If \(p\), \(q\), \(x\), and \(y\) are positive integers, is \(\frac{q^y}{p^x}\) an integer?


(1) \(q\) is evenly divisible by \(p\)

(2) \(y \ge x\)
[Reveal] Spoiler: OA

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The question asks if we can determine whether the expression \(\frac{q^y}{p^x}\) yields an integer. This is the same as asking if \(q^y\) is divisible by \(p^x\) or, equivalently, if \(p^x\) is a factor of \(q^y\).

Statement 1 tells us that \(q\) is evenly divisible by \(p\), or, in other words, that \(p\) is a factor of \(q\). Let us plug in numbers that satisfy this condition and see if we can answer the question in the prompt. We will choose \(p = 2\) and \(q = 4\). However, since we are given no information on \(x\) or \(y\), we can plug in any integer values for \(x\) and \(y\). If \(x = 3\) and \(y = 1\), then \(\frac{q^y}{p^x} = \frac{4^1}{2^3} = \frac{4}{8} = \frac{1}{2}\), which is not an integer. On the other hand, if \(y = 3\) and \(x = 1\), \(\frac{q^y}{p^x} = \frac{4^3}{2^1} = \frac{64}{2} = 32\), which is an integer. Statement 1 alone is NOT sufficient to answer the question. Eliminate answer choices A and D. The correct answer choice is B, C, or E.

Statement 2 tells us that \(y \ge x\). However, we know nothing about the values of \(p\) and \(q\), which can be any integers. Whether the expression yields an integer depends on the relationship between \(p\) and \(q\). Statement 2 alone is also NOT sufficient to answer the question. Eliminate answer choice B. The correct answer choice is either C or E.

Taking both statements together: Statement 1 tells us that \(p\) is a factor of \(q\), which implies that \(p \le q\), and statement 2 tells us that \(x \le y\). This means that the term \(q^y\) will always be larger than \(p^x\), and since \(p\) is a factor of \(q\), \(\frac{q^y}{p^x}\) will always yield an integer. For example, if \(p = 3\), \(q = 6\), \(x = 1\), and \(y = 2\), then \(\frac{q^y}{p^x} = \frac{6^2}{3^1} = \frac{36}{3} = 12\). Both statements together are sufficient.


Answer: C
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Collection of Questions:
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Re: S95-05 [#permalink]

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New post 03 Feb 2017, 10:18
if in this solution q = 6, p = 3 , y = 3 and x = x (y>=x). Then answer is 2 raised to power of 1.5, which is not integer. so answer should be neither is sufficient.

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New post 03 Feb 2017, 12:57
kriti2016 wrote:
if in this solution q = 6, p = 3 , y = 3 and x = x (y>=x). Then answer is 2 raised to power of 1.5, which is not integer. so answer should be neither is sufficient.


Please note that the OA for this question is C, not E. So, you must be wrong somewhere. If you clarify what you mean by the red part I might be able to tell you where you went wrong.
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Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Kudos [?]: 118450 [0], given: 11999

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Re: S95-05 [#permalink]

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New post 30 Apr 2017, 07:19
kriti2016 you would not get a fraction for the power ie. 1.5 since all variables are intergers

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Re: S95-05   [#permalink] 30 Apr 2017, 07:19
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